Wappalyzer

Wappalyzer is a browser extension that uncovers the technologies used on websites. It detects content management systems, web shops, web servers, JavaScript frameworks, analytics tools and many more.
List of applications Wappalyzer detects:
http://wappalyzer.com/applications
Firefox version:
https://addons.mozilla.org/en-US/firefox/addon/wappalyzer/
Bug reports and suggestions:
https://github.com/dashboard/issues
Wappalyzer has been made possible by AOE media GmbH, the leading Open Source web development company in Germany.